Method of producing of cellulose ester film

ABSTRACT

In order to produce a cellulose ester film constructed of a front layer, an intermediate layer and a rear layer, a dope solution is doped on a supporter. In at least one of the front layer and the rear layer, a mass ratio of a cotton linter to a wood pulp (cotton linter/wood pulp) is between 5/95 and 0/100, and a solvent of the dope contains more than 15 wt.% alcohols and hydrocarbons whose carbon number each is 1-10. Further, a ratio of a solid content density of a solution for forming the front layer and the rear layer to a solid density of a solution for forming the intermediate layer is less than 0.9 wt.%, and a total thickness of the solutions for front and rear layers is more than 5% of the dope ribbon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of producing of a celluloseester film which is used for a deflector protect film and an opticalcompensation film.

2. Description Related to the Prior Art

A deflector protect film and an optical compensation film are producedof a cellulose ester film, such as cellulose triacetate film(hereinafter TAC film) and the like. The TAC film is produced in amethod for producing a film from a solution. In the method additives aresolved in a solvent to produce a high molecular solution (dopesolution), and thereafter the dope solution is doped on a supporter witha die having a slit, dried for a predetermined time, peeled from thesupporter, and further dried again to produce the TAC film.

When the dope solution is dried for a long time thereby, the solvent inthe dope solution is evaporated to form a skinning of high molecularmaterial on both edges of the slit of the die. The skinning prevents thedoping of the dope solution, and causes the thickness in both edges ofthe dope solution on the supporter to become uneven. Further sometimesthe skinning falls down from the both edges of the slit of the die. Inthis case, the skinning adheres on a feed roller to damage the TAC filmdried from the dope solution on the supporter. In order to prevent thegeneration of the skinning, U.S. Pat. No. 3,112,528, Japanese PatentLaid-Open Publications No. 2-208650 and 5-86212 describe methods inwhich the solvent is flown to solve solutes in the dope solution or amixture of the evaporated solvent and air are blown.

However, in the above methods, the amount of the mixture and the solventis hardly regulated. Accordingly vibration of edges of a dope ribbonbetween the die and the supporter causes to generate the skinning.

Further, the deflector protect film is applied to one of both side of adeflector. The deflector is formed of a polyvinylalcohol film(hereinafter PVA film). The PVA film is extended on a shaft for dieingin iodine or to color dyne, and otherwise after dying the PVA film isextended, and bridges with boron compound to produce the deflector.

Several types of the cellulose ester films are proposed. For example,Japanese Patent Laid-Open Publication No. 6-134933 proposes a cellulosetriacetate laminate film having a cellulose triacetate film producedfrom cotton and pulp for easy peeling and improving the heat resistance.Further, Japanese Patent Laid-Open Publication No. 2000-19776 proposes acellulose ester film whose averaged substitution degree is 2.88-3.00 toalways prevent the generation of optical creases.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of producing acellulose ester film, in which the generation of a skinning isprevented.

Another object of the present invention is to provide a method ofproducing a cellulose ester film used for a deflector protect film andan optical compensation film.

Still another object of the present invention is to provide a method ofproducing the cellulose ester film used for deflector plate, in whichoptical non-uniformity does not occur in edges of a corner of a liquidcrystal indicator with a deflector to which a deflector protect film isapplied

In order to achieve the objects and other objects, in a method of thepresent invention for forming the cellulose ester film having front,intermittent and rear layers, the dope solution to be doped on asupporter is composed of a first solution for forming the front layer, asecond solution for forming the intermittent layer and the thirdsolution for forming the rear layer. A ratio A/B of a shearing viscosityA of the first or third solution to a shearing viscosity B of the secondsolution is under 0.9.

Further, in a second embodiment of the method of the present invention,the cellulose ester film is produced by using a die having pluralmanifolds, and each manifold contains a solutions. The dope solution iscomposed of the solutions and doped on a supporter. The solvent of thedope solution is alcohol having 1-10 carbons and included 15 wt. %hydrocarbon. The dope solution is dried on the supporter to form thecellulose ester film, and then the cellulose ester film is peeled fromthe supporter. Thereafter, the cellulose ester film is dried such thatin at least one of surface layers of the plural layers a ratio of cottonlinter and wood pulp is between 5 to 95 and 0 to 100.

By doping the dope solution, a total thickness of the solutions for thesurface layers is more than 5% of the thickness of a dope ribbon.Furthermore, to the dope solution is fed a mixed solvent containing abad solvent between 30-90% to a solute of the dope solution.

In the third embodiment of the method of the present invention, the dieprovided with a feed block is used for doping the dope solution to formthe cellulose ester film having plural layers. In the forth method ofthe present invention, plural dies are used for doping the dopesolutions so as to form a same number of layer in the cellulose esterfilm as the dies.

According to the present invention, it is prevented to generate anoptical skinning in a corner of a liquid crystal indication device andcreases on an end of a slit. Further, the quality of the cellulose esterfilm becomes higher.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomeeasily understood by one of ordinary skills in the art when thefollowing detailed description would be read in connection with theaccompanying drawings:

FIG. 1 is a schematic diagram of a device for producing a celluloseester film;

FIG. 2A is a sectional view of the cellulose ester film;

FIG. 2B is a sectional view of the cellulose ester film;

FIG. 3A is a sectional view of the cellulose ester film having a surfacelayer;

FIG. 3B is a sectional view of the cellulose ester film having twosurface layers;

FIG. 4 is a side view of a die and a feed block;

FIG. 5A is a sectional view of a part of the die in a situation ofdoping a dope solution;

FIG. 5B is a schematic sectional view of the feed block;

FIG. 6A is a sectional view of a dope ribbon;

FIG. 6B is an exploded sectional view of an edge of the dope ribbon;

FIG. 7 is an exploded sectional view of a die having three manifolds;

FIG. 8 is an exploded sectional view of three dies;

FIG. 9 is a schematic view of a doping section and a drying section ofthe second embodiment;

FIG. 10 is a schematic view of a doping section and a drying section ofthe third embodiment;

FIG. 11 is a schematic view of a doping section and a drying section ofthe forth embodiment;

FIG. 12 is a schematic view of a doping section and a drying section ofthe fifth embodiment;

FIG. 13 is a schematic view of a doping section and a drying section ofthe sixth embodiment;

FIG. 14 is a schematic view of a doping section and a drying section ofthe seventh embodiment;

FIG. 15 is a schematic view of a doping section and a drying section ofthe eighth embodiment;

FIG. 16 is a schematic view of a doping section and a drying section ofthe ninth embodiment;

FIG. 17 is a schematic view of a doping section and a drying section ofthe tenth embodiment.

PREFERRED EMBODIMENTS OF THE INVENTION

[Polymer]

As high molecular material (polymer) used for a dope solution of thepresent invention, there are polyamides, polyolefines (for examplenorbornene polymers and the like), polystyrenes, polycarbonates,polysulfates, polyacrylates, polymehtacrylic acids (for examplepolymethylmethacrylate and the like), polyetheretherketones, polyvynilalcohols, polyvynil acetates, cellulose derivatives (low fatty acidesters of cellulose and the like). The low fatty acid esters ofcellulose (cellulose acylate) are especially preferable.

A low fatty acid of the low fatty acid ester of cellulose has less than6 carbons. The preferable number of the carbon is 2 (cellulose acetate),3 (cellulose propionate) or 4 (cellulose butylate). The celluloseacetate is much preferable and the cellulose triacetate (Acetificationdegree: 58.0-62.5%) is especially preferable. Further a mixture of fattyacid esters may be used, for example, cellulose acetate propionate andcellulose acetate butylate.

[Solvent]

According to solvent, organic solvent is preferable to inorganic one. Asthe organic solvent, there are hydrocarbon chloride (methylenechloride), ketones (for example acetone, methylethylketone,cycrohexanone and the like), esters (methylfolmate, methyl acetate,ethyl acetate, amyl acetate, butyl acetate and the like), ethers (forexample dioxane, dioxorane, tetrahydrofrane, dyethyl ether,methyl-t-butyl ether and the like), aromatic hydrocarbon (for examplebenzene, toluene, xylene and the like), fatty hydrocarbons (for examplehexane and the like), and alcohols (for example methanol, ethanol,n-propyl alcohol, isopropyl alcohol, n-butanol and the like).

The solvent is preferably swollen. Accordingly, the sort of the solventsis determined in accordance with polymers which are used. For example,when as the polymer cellulose triacetate, polycarbonates and polyestersare used, acetone or acetylic acid methyl is used as a preferablesolvent. Further, benzene, toluene, xylene, hexane, acetone,methylethylketone are preferably used for norbornen polymers.Furthermore, acetone, methylethylketone, methylacetate, butylacetate ormethanol are used for polymethylmethacrylate. Note that more than twokinds of solvents may be mixed and used.

Considering to harmful influences on human bodies and circumstances,materials containing chlorine, such as methylenechloride, may not beused. For producing the dope solution, ketones and alcohols may bemixed. Especially when cellulose acylate is used as polymer, methylacetylate is preferably used as it easily solves. Further, acetylic acidmethyl may more easily solve in mixture of ketones and alcohols. In thiscase, according to a ratio of each solvent, acetylic acid methyl is20-90 wt. %, ketones are 50-60 wt. %, and alcohols are 5-30 wt. %.

A boiling point of solvent composing the dope solution is preferably20-300° C., particularly 30-200° C., especially 40-100° C.

[Additives]

Plasticizer, ultraviolet absorptive material, deterioration inhibitormay be added as the additives to the dope solution.

(Plasticizer)

As the plasticizer used in the present invention, there are phosphoricacid ester plasticizer (for example triphenylphosphate,tricresylphosphate, cresyldiphenyl phosphate, octyldiphenylphosphate,diphenylbiphenyl phosphate, trioctylphosphate, tributylphosphate and thelike), phthalic acid ester plasticizer (for example diethylphthalate,dimethoxyethylphthalate, dimethylphthate, dioctylphthalate and thelike), grycolic acid ester plasticizer (for example triacetine,tributyline, butylphthalylbutylbricolate, ethylphthalylethylgricolate,methylphthalylethylgricolate, butylphthalylbutylgricolate and the like).Some of the plasticizer may be mixed. Further, other plasticizersdescribed in Japanese Patent Laid-Open Publication No. 11-80381,11-124445, 11-248940 may be also used. The plasticizers are preferablycontained 0.1-20 wt. % to the polymer in the dope solution, particularly6-16 wt. %.

(Ultraviolet Absorptive Material)

Ultraviolet absorptive materials may be added in the dope solution.Especially the dope solution may contain one or more sorts ofultraviolet absorptive materials. A film produced in a method of thepresent invention is often used as an optical material for liquidcrystal monitor. In this case, the ultraviolet absorptive materialshould effectively absorb ultraviolet ray under 370 nm of wave length inview of preventing deterioration of the liquid crystal, and hardlyabsorb visible ray above 400 nm of wave length in view of indicationprobability of the liquid crystal. For example, there areoxybenzophenone compounds, benzotriazol compounds, salycilic acid estercompounds, bensophenone compounds, cyanoacrilate compounds, nickelcomplex salt compound, and the like. Particularly preferable arebenzotriazol compounds and benzophenone compounds. Especiallybenzophenone compound hardly makes a unnecessary coloring of thecellulose ester. The benzotriazol ultraviolet compounds include thosedescribed in Japanese Patent Laid-Open Publication 8-29619. Further,ultraviolet absorptive materials already known, such as described inJapanese Patent Laid-Open Publication No. 8-23950, may be also used. Theultraviolet absorptive material is preferably contained in 0.001-5 wt.%.

As the preferable ultraviolet absorptive material, there are, forexample, 2,6-di-tert-butyl-p-crezol,pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],triethylenegrycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate],1,6-hexanediol -bis[3-3,5-di-tert-butyl-4-hydroxyphenyl propionate],2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)1,3,5-triazine,2,2-thio-diethylene-bis[3-(3,5-di-tert-butyl-4-hydrozypheny)propionate],Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,N,N′-hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocynenamide),1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydrozybenzil)benzene,tris-(3,5-di-tert-butyl-4-hydroxybenzil)-isocianulate.

Especially preferable are 2,6-di-tert-butyl-p-crezol,pentaerythrytyl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate],triethyleneglycol-bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate].Metal deactivators of hydradine compounds, for example,N,N′-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydradine, andphosphate processing stabilizer, such astris(2,4-di-tert-butylphenyl)phosphite may be mixed and used. Suchcompounds are preferably contained in 0.001-5 wt. % to the polymer inthe dope solution.

(Particle Powders)

The dope solution preferably contains mat materials of particle powdersfor improving an adhering endurance property under high moisture of thefilm. A height of protrusions on a surface of the mat material ispreferably 0.005-10 μm, particularly 0.01-5 μm. The number of theprotrusions is preferably large. However, when it is larger thannecessary, the protrusions cause to generate haze. The mat materials maybe inorganic and organic and may be sometimes formed in ball-shape inspray-dry method or diffusing method. As inorganic mat materials, thereare barium sulfate, manganese colloid, titanium dioxide, bariumstrontium sulfate, silicon dioxide, aluminum oxide, zinc oxide, tinoxide, calcium carbonate, talc, caoline, calcium sulfate. Further, thereare silicone dioxide, (for example synthetic silica obtained by gelatingsilicic acid of in wet processing) and titanium dioxide produced fromtitanslag and sulfuric acid. The inorganic mat material may be obtainedalso by milling inorganic compound whose diameter is more than 20 mm.Thereafter, the classification of inorganic compound is carried out forexample by (vibrating filtration, wind power classification).

As the organic compound, there are polytetrafluoroethylene, celluloseacetate, polystyrene, polymethylmethacrilate, polypropylmethacrilate,polymethyl acrilate, polyethylene carbonate, acrylstyrene resins,silicone resins, polycarbonate resins, benzoguanamine resins, melanineresins, polyolefin resins, polyamide resins, polyimide resins,polyfluoroethylene resins and starch. There are further high molecularcompound synthesized in suspension polymerization. However, when theamount of the particle powders is too large in the dope solution, theresiliency of the film becomes lower. Accordingly, the dope solutionpreferably contain the particle powders in 0.001-5 wt. % to the polymer.

[Fluoride Surface-active Agent]

In the dope solution, fluoride surface-active agents may be also added.The fluoride surface-active agents have a hydrophobic group offluorocarbon chain, and is used as coating agent in organic solvent or aantistatic agent while it decreases a surface tension. As the fluoridesurface-active agent there are, for example, C₈F₁₇CH₂CH₂O—(CH₂CH₂O)₁₀—OSO₃Na,

-   C₈F₁₇SO₂N(C₃H₇) (CH₂CH₂O)₁₆—H,-   C₈H₁₇SO₂N(C₃H₇)CH₂COOK, C₇F₁₅COONH₄,-   C₈H₁₇SO₂N(C₃H₇)CH₂CH₂O)₄—(CH₂)₄—SO₃Na,-   C₈H₁₇SO₂N(C₃H₇) (CH₂)3-N⁺(CH₃)₃I⁻,-   C₈F₁₇SO₂N(C₃H₇)CH₂CH₂CH₂N⁺(CH₃)₂—CH₂COO⁻, C₈F₁₇CH₂CH₂O(CH₂CH₂O)₁₆—H,-   C₈F₁₇CH₂CH₂O(CH₂)₃—N⁺(CH₃)₃I⁻,-   H(CF₂)₈—CH₂CH₂OCOCH₂CH(SO₃)COOCH₂CH₂CH₂—(CF₂)₈—H-   H(CF₂)₆CH₂CH₂O(CH₂CH₂O)₁₆—H,-   H(CF₂)₈CH₂CH₂OCOCH₂CH(SO₃)COOCH₂CH₂CH₂CH₂C₈F₁₇,-   C₉F₁₇—C₆H₄—SO₂N(C₃H₇) (CH₂CH₂O)₁₆—H,-   C₉F₁₇—C₆H₄—CSO₂N(C₃H₇) (CH₂)C—N⁺(CH₃)₃I⁻.    The amount of the fluoride surface active agent in the dope solution    is preferably 0.001-2 wt. % to the polymer.

Further, in the dope solution, several sorts of the additives may beadded to the solution. As the additives there are thermostabilizer,antistatic agent, flame retardant, lubricant, oils and the like that arefor example salt of alkali earth metal such as calcium and magnesium.

[Mold Releasing Agent]

In the dope solution, a mold releasing agent may be added. The dopesolution is doped on a supporter and dried thereon to the film. Byadding the mold releasing agent, the film may be easily peeled from thesupporter. As the mold releasing agent, there are waxes having highmelting point, high fatty acid, salts and esters thereof, silicone oil,polyvinyl alcohol, low molecular polyethylene, plant protein derivativesand the like. The amount of the molding releasing agent is preferably0.002-2 wt. % to the polymer in the dope solution not so as to harmfullyinfluence on luster and smoothness of the surface of the film.

[Mold Releasing Accelerator]

In the dope solution, a mold releasing accelerator may be added. As themold releasing accelerator, surface-active agents are especiallypreferable, and described in Japanese Patent Laid-Open Publication No.61-243837. There are phosphorus type, carbon type, nonionic type,cationic type and the like in the surface active agent. The amount ofthe molding releasing accelerator is 0.002-2 wt. %, preferably 0.005-1wt. %, especially 0.01-0.5 wt. %.

The mold releasing accelerators are described as follows:(R₁—B₁—O)_(n1)—P(═O)—(OM₁)_(n2)  Formula (1)R₂—B₂—X  Formula (2)

Herein R₁ and R₂ are alkyl group, alkenyl group, alarkyl group and arylgroup; M₁ is alkali earth metal, ammonia, lower alkylamine. B1and B2 arecoupling group of two valencies; X is carbonic acid (or salt thereof),sulfenic acid (or salt thereof) and sulfuric acid ester (or saltthereof). n1 is the number of “1” or “2”, and n2 is integer of (3−n1).

Preferable examples of R₁ and R₂ are non-substituted alkyl group whichhas 4-40 carbons (butyl, hexyl, octyl, 2-ethylhexyl, nonyl, dodecyl,hexadecyl, octadecyl, eicosanyl, docosanyl, myricyl and the like),non-substituted alkenyl group which has 4-40 carbons (2-hexenyl,9-decenyl, oleyl and the like), substituted and non-substituted arylgroup which has 4-40 carbons (phenyl, naphtyl, methylphenyl,dimethylphenyl, trimethylphenyl, ethylphenyl, propylphenyl,di-isopropylphenyl, tri-isopropylphenyl, t-butylphenyl,di-t-butylphenyl, tri-t-butylphenyl, isopentylphenyl, ectylphenyl,isooctylphenyl, isononylphenyl, diisononylphenyl, dodecylphenyl,isopentadecylphenyl and the like).

Especially preferable are hexyl, octyl, 2-ethylhexyl, nonyl, dodecyl,hexadecyl, octadecyl, docosanyl, alkenyl, phenyl, naphtyl,tri-methylphenyl, di-isopropylphenyl, tri-isopropylphenyl,di-t-butylphenyl, tri-t-butylphenyl, isooctylphenyl, isononylphenyl,di-isononylphenyl and dodecylisonetadecylphenyl.

B₁ and B₂ are alkylene having 1-10 carbons, polyoxiethylene (degree ofpolymerization: 1-50), polyoxipropylene (degree of polymerization:1-50), polyoxiglycerin and a mixture thereof. Preferable examples of B₁and B₂ are methylene, ethylene, propylene, butylenes, polyoxiethylene(degree of polymerization: 1-25), polyoxipropylen (degree ofpolymerization: 1-25), polyoxiglicerin (degree of polymerization: 1-15).Preferable examples of X are sulfonic acid, sulfuric acid ester, andtheir salt with Na, K, ammonium, trimethylamine and triethanolamine.

The preferable embodiments of the mold releasing accelerators arerepresented in the following formulars:C₈H₁₇O—P(═O)—(OH)₂  RZ-1C₁₂H₂₅O—P(═O)—(OK)₂  RZ-2C₁₂H₂₅OCH₂CH₂O—P(═O)—(OK)₂  RZ-3C₁₅H₃₁(OCH₂CH₂)₅O—P(═O)—(OK)₂  RZ-4{C₁₂H₂₅O(CH₂CH₂O)₅}₂—P(═O)—OH  RZ-5{C₁₈H₃₅(OCH₂CH₂)₈O}₂—P(═O)ONH₄  RZ-6(t-C₄H₉)₃—C₆H₂—OCH₂CH₂O—P(═O)—(OK)₂  RZ-7(iso-C₉H₁₉—C₆H₄—O—(CH₂CH₂O)₅—P(═O)—(OK)OH  RZ-8C₁₂H₂₅SO₃Na  RZ-9C₁₂H₂₅OSO₃Na  RZ-10C₁₇H₃₃COOH  RZ-11C₁₇H₃₃COOH.N(CH₂CH₂OH)₃  RZ-12iso-C₈H₁₇—C₆H₄—O—(CH₂CH₂O)₃—(CH₂)₂SO₃Na  RZ-13(iso-C₉H₁₉)₂C₆H₃—O—(CH₂CH₂O)₃—(CH₂)₄SO₃Na  RZ-14sodium triisopropylnaphthalenesulfonate  RZ-15sodium tri-t-butylnaphthalenesulfonate  RZ-16C₁₇H₃₃CON(CH3)CH₂CH₂SO₃Na  RZ-17C₁₂H₂₅—C₆H₄SO₃.NH₄  RZ-18

Further, Japanese Patent Laid-Open Publication No. 10-316701 describesacids and salts thereof as the preferable examples of the mold releasingaccelerator. Acid dissociaion constant pKa of the acids and salts is1.93-4.50, preferably 2.0-4.4, particularly 2.2-4.3 and especially2.6-4.3.

The acid may be organic or inorganic acid. As the inorganic acid, thereare, for example, HClO₂ (2.31), HOCH (3.48), Molybdic acid (H₂, MoO₄:3.62), HNO₂, (3.15), phosphoric acid (H₃, PO₄: 2.15), tri-polyphosphoricacid (H₅, P₃, O₁₀: 2.0), vanadic acid (H₃, VO₄: 3.78) and the like. Asthe organic acid, there are fat group monocarbonic acids, such as formicacid (3.55), oxaluric acid (2.27), cyanoacetic acid (2.47), phenylaceticacid (4.10), phenoxyacetic acid (2.99), fluoroacetic acid (2.59),chloroacetic acid (2.69), bromoacetic acid (2.72), iodoacetic acid(2.98), mercaptoacetic acid (3.43), vinylacetic acid (4.12),chloropropionic acid (2.71-3.92), 4-aminobutyric acid (4.03) and acrylicacid (4.26). High fatty carbonic acids may be also used, for example,malonic acid (2.65), succinic acid (4.00), glutaric acid (4.13), adipicacid (4.26), pimelic acid (4.31), azelatic acid (4.39), fumalic acid(2.85), grycolic acid (3.63), lactic acid (3.66), malic acid (3.24),tartaric acid (2.82-2.99), citric acid (2.87) and the like. There arefurther glyoxylic acid (3.18), pyrvic acid (2.26), levulinic acid(4.44), anilinesulfonic acid (3.74-3.23), benzoic acid (4.20),aminobenzoic acid (2.02-3.12), chlorobenzoic acid (2.92-3.99),cyanobenzoic acid (3.60-3.55), nitrobenzoic acid ((2.17-3.45),hydroxybenzoic acid (4.08-4.58), anisic acid (4.09-4.48), fluorobenzoicacid (3.27-4.14), bromobenzoic acid (2.85-4.00), iodobenzoic acid(2.86-4.00), salicylic acid (2.81), naphtoic acid (3.70-4.16), cinnamicacid (3.88), mandelic acid (3.19), phthalic acid (2.75), isophthalicacid (3.50), telephthalic acid (3.54), nicotinic acid (2.05),2-furancarboxylic acid (2.97), 2,6-pyridinecarboxylic acid (2.09) andthe like.

As the mold releasing accelerator there are amino acids, such asasparatgine (2.14), aspartic acid (1.93), adenine (4.07), alanine(2.30), b-alanine (3.53), arginine (2.05), isoleucine (2.32), glycine(2.36), glutamine (2.17), glutamic acid (2.18), serine (2.13), tyrosine(2.17), tryptophane (2.35), threonine (2.21), norleucine (2.30), valine(2.26), phenylalanine (2.26), methionine (2.15), lysine (2.04) andleucine (2.35). There are also amino acid derivatives, such as adenosine(3.50), adenosine triphosphate (4.06), adenosine phosphate (3.65-3.80),L-alanyl-L-alanine (3.20), L-alanylglycine (3.10), b-alanylglycine(3.18), L-alanylglycyrglycine (3.24), b- alanylglycyrglycine (3.19),L-alanylglycyrglycyrglycine (3.18), glycyr-L-alanine (3.07),glycyr-b-alanine (3.91), glycyrglycyr-L-alanine (3.18),glycyrglycyrglycine (3.20), glycyrglycyrglycyrglycine (3.18),glycyrglycyr-L-histidine (2.72), glycyrglycyrglycyr-L-histidine (2.90),glycyr-DL-histidylglycine (3.26), glycyr-L-histidine (2.54),glycyr-L-leucine (3.09), g-L-glutamine-L-cicteinylglycine (2.03),N-methylglycine (sarcosine: 2.20), N,N-dimethylglycine (2.08),cytllurine (2.43), 3,4-dihydroxiphenylalanine (2.31), L-histidilglycine(2.84), L-phenylalanilglycine (3.02), L-propylglycine (3.07),L-leucil-L-tyrosine (3.15).

Preferable are formic acid, chloroacetic acid, haloacetic acid,halopropionic acid, acrylic acid, moronic acid, succinic acid, glutaricacid, fumalic acid, glycolic acid, lactic acid, malic acid, tartaricacid and citric acid.

These acids may be used as free acid, and their salts with alkali metal,alkali earth metal and heavy metal. As alkali metal, there are lithium,potassium, and preferably sodium. As alkali earth metal, there arebarium, strontium, preferably calcium, magnesium. As heavy metal thereare zinc, tin, nickel and iron. Note that one or more than two sorts ofthe metals may be used.

In 1 g of cellulose ester, the acid and the salt thereof may be1×10⁻⁹-3×10⁻⁵ mol, preferably 1×10⁻⁸-2×10⁻⁵, particularly 1×10⁻⁷-1×10⁻⁵,and usually 5×10⁻⁷-5×10⁻⁶. The amount of the acids and salts in thecellulose esters may be determined with ionchromatography analysis.

[Ionchromatography Analysis]

2.0 g of powders of dried cellulose acetate is measured. Hot water 80 mlis added to the cellulose acetate to produce a mixture of the hot waterand the cellulose acetate. The mixture is agitated and left for a nightin a tightly closed case. Thereafter, the mixture is agitated again andleft for a while. Then the uppermost solution is obtained as a samplesolution.

Note that the alkali metal and the alkali earth metal, if their amountin the solution is not large, may be bound with acid group of thecellulose acetate. Total amount of alkali metal and alkali earth metalin cellulose acetate 1 g is determined not so as to have a bad influenceon heat resistance stabilization. Namely, the total amount is, in ionequivalent amount, less than 5.5×10⁻⁶, preferably 3.5×10⁻⁶, particularly2.5×10⁻⁶. Especially, the total amount is less than 1×10⁻⁶, moreespecially less than 0.3×10⁻⁶. In this case, when the film ishalf-dried, the film is easily peeled from the supporter without damage.The amount of the alkali metal and alkali earth metal is determined withatomic absorption analysis.

The mold releasing accelerators (1) and (2) are produced by mixingcellulose acetate with acids and salts of acid dissociation constantpKa. Thereby the acids and the salts may be processed with the celluloseacetate during or after a process, such as a producing process of thecellulose acetate. The powdered or flaked cellulose acetate is cleansedor dipped in water or a solution. Further, the acids and the salts maybe added in the dope containing the cellulose acetate. The processingthe cellulose acetate with the acids and the salts are preferablycarried out in 10-70° C., preferably 15-50° C., for 1minute-12 hours.Thus the cellulose acetate can continuously have at least a carboxylicgroup even after the processing.

A method of producing a film from the cellulose ester is explained now.

In FIG. 1, there are three dope preparing sections 15. each of the dopepreparing section 15 has a mixing tank 1, a feed pump 2 and a filter 3.The mixing tank 1 is used for preparing the dope. In the mixing tank 1,the cellulose triacetate and the additives are mixed. The mixing tank 1is connected through the feed pump 2, the filter 3 and a feed block 32to a die 4 of a doping section 16. The doping section 16 is constructedof the die 4, a supporter a rotary drums 6, 7 and plural guide rollers8. Below the die 4, the rotary drums 6, 7 and a belt 5 are disposed. Thebelt 5 is used as the supporter, and is extendedly set the rotary drums6, 7 so as to confront to the die 4. From the die 4 the dope solution isprovided on the belt 5. Further, above and below the belt 5, a dried airblow supplier (not shown) is provided that is used for drying the dopesolution on the belt 5. Thus the dope solution dried to become the film.

The rotary drum 6 is confronted to a peeling roller 9 of a dryingsection 17. The film is peeled from the supporter by the peeling roller9. The drying section has further guide rollers 10 and a drying room 12.In the drying section the film is perfectly dried and thereafter woundon a winding roller 11.

Before forming the film, the solvent evaporates. If P and Q aredetermined as weights of the dried film and the solvents respectively,the remain-evaporate ratio of the film is represented in R=(Q/P)×100.The remain-evaporate ratio R is preferably more than 120%, andparticularly 200%. Further, the film may be dried after remove from thesupporter.

When the remain-evaporate ratio R is less than 120 wt. %, only one ofthe surfaces of the film is dried, and the film is hardly wound.Therefore, before winding, the film is dried again.

Further, it is preferably to carry out the nailing in the film and cutdown edges of the film before winding.

In FIG. 2A, a film 21 has an outer part 21 a which is made from asolution containing cotton linter and wood pulp in ratio (cottonlinter/wood pulp) 5/95-0/100. The solution contains as its solvent morethan 15 wt. % alcohol and hydrocarbons whose number of carbon is 1-10.In FIG. 2B, a film 21 further has an outer part 21 b which is made froma solution containing cotton linter and wood pulp in ratio (cottonlinter/wood pulp) 5/95-0/100. The solution contains as its solvent morethan 15 wt. % alcohol and hydrocarbons whose number of carbon is 1-10.

In FIG. 3A, a film 22 has a two-layers structure. A surface layer 22 aof the film 22 is made from a solution containing cotton linter and woodpulp in ratio (cotton linter/wood pulp) 5/95-0/100. The solutioncontains as its solvent more than 15 wt. % of alcohol and hydrocarbonswhose number of carbon is 1-10. In FIG. 3B, a film 22 has a three layerstructure. A surface layer 22 b of the film 22 is made from a solutioncontaining cotton linter and wood pulp in ratio (cotton linter/woodpulp) 5/95-0/100. The solution contains as its solvent more than 15 wt.% alcohol and hydrocarbons whose number of carbon is 1-10.

Note that the present invention is not restricted in the embodimentillustrated in FIG. 2A, 2B, 3A and 3B, and may have four layerstructure, for example.

In FIG. 4, the die 4 is provided with a nozzle 60, vessel 62 and a pump63. The vessel 62 contains a mixture solvent (not shown) of good and badsolvents of cellulose triacetate. The mixture solvent is fed out throughthe nozzle 60 by the pump 63.

In FIG. 5A, the die 4 is a feed block type. The supporter 33 moves at apredetermined speed in an arrowed direction, and the die 4 dopes thedope solution as a dope ribbon 31 on the belt 5. As shown in FIG. 5B,the feed block 32 is supplied with solutions 33 a, 33 b, 33 c, and has astructure to superpose them. Accordingly, the dope ribbon 31 has athree-layers structure.

The solutions 33 a, 33 c are mixed with the mixture solvent fed out fromthe nozzle 60. Accordingly the dope ribbon 31 does not vibrate and edgesof the dope ribbon become stable. As the bad solution there aremethanol, n-butanol and the like, and as the good solution there aremethylene chloride, methylacetate, and the like. Further, the solidcontent density of the solutions 33 a and 33 c becomes lower to preventthe skinning in the edges of the film.

As shown in FIG. 6A, the dope ribbon 31 is constructed of a first layer31 a, a second layer 31 b and a third layer 31 c. The second layer 31 bis sandwitched by the first and second layer 31 a, 31 c. As shown inFIG. 6B, in an edge of the dope ribbon 31 the first layer 31 a and thirdlayer 31 c becomes thicker. When D, S1 and S2 are determined asthickness of the dope ribbon 31, the first layer 31 a and the thirdlayers 31 c respectively, the following formula should be satisfied:(S1+S2)D×100>5 (%)

In FIG. 7, a die 40 may have three manifolds 41 a, 41 b, 41 c. Themanifolds 41 a, 41 b, 41 c are provided with solutions 33 a, 33 b, 33 crespectively, and in the die 40 the three layer dope 31 is constructed.

Note that a solid content density of the solutions 33 a, 33 cconstructing outer sides of the three layer dope 31 is preferably by0.5% lower than that of the solution 33 b constructing a core layer ofthe three layer dope 31. Otherwise, the film may have slight projectionsor retractions on a surface thereof to cause damages in the edges of thefilm.

In the present invention, the alcohols and hydrocarbons having 1-10carbons are preferably contained more by 1 wt. %, particularly by 2 wt.% in the solution 33 c than in the solutions 33 a, 33 b. Otherwise, itbecomes hard to peel the film from the belt 5.

The temperature of a surface of the belt 5 is preferably between −20° C.and 25° C., particularly between −10° C. and 15° C. When the temperatureof the surface is below −20° C., a gas solidalization often occurs todamage the surface of the film. When the temperature of the surface isover 25° C., bubbles often generate and the film easily sticks on thebelt 5 to cause the forming of slight projections and retractions.

In FIG. 8, three dies 50 a, 50 b, 50 c may be used. The three dies 50 a,50 b, 50 c are supplied with the solutions 33 a, 33 b, 33 c to dope themon the supporter respectively. Thus the solution 33 a lies on the belt5, the solution 33 a lies uppermost, and the solution 33 c issandwitched between the solutions 33 a and 33 c.

In FIG. 9, the drying section 17 is further provided with a tenter 84between the peeling roller 9 and the drying chamber 12. By the tenter84, the film is stretched and dried. As shown in FIG. 10, heater platesare provided above and below the belt 5 to effectively dry the dope.Further, in FIG. 15 a drum 82 is used as the supporter.

In FIG. 12, the drying section has a drying chamber 13 too. As shown inFIG. 13, the tenter 84 may be disposed between the drying chambers 12,13. In FIG. 14 the heater plates 83 are disposed above and below thebelt 5, and in FIG. 15 a die 85 is provided so as to confront to thedrum 7. In FIG. 16 the drum 82 is used as the supporter, and in FIG. 17,a heater 85 is provided so as to confront to the drum 82.

A method of producing the film from the cellulose ester is notrestricted in them. For example the die 4 may be provided with apressure reduction chamber.

[Preparation of Solutions Constructing Dope Solution]

Preparation of solutions is explained as an example in which cellulosetriacetate is used as the polymer.

In the dope ribbon 31, the solid content density of the solution 33 bfor the intermediate layer 31 b in the dope ribbon 31 is preferably15-30 wt. %, especially 18-27 wt. %, and that of the solutions 33 a, 33c for the front and rear layers 31 a, 31 c is preferably 10-25 wt. %,especially 13-22 wt. %.

(Swelling Process)

Cellulose triacetate particles and solvents are mixed to produce a mixedsolution. Thereafter, the cellulose triacetate particles are swollen inthe solvent. A temperature therefore is preferably between −10 and 55°C., and usually set in a room temperature. A ratio of the cellulosetriacetate to the solvent is determined in accordance with alayer-structure in the cellulose triacetate film.

The solution 33 b for the intermediate layer 31 b preferably containscellulose triacetate between 13 and 27 wt. %, particularly between 16and 25 wt. %, especially between 19 and 23 wt. %. The solutions 33 a, 33c for the front and rear layers 31 a, 31 c preferably contain cellulosetriacetate between 9 and 23 wt. %, particularly between 12 and 21 wt. %,especially between 15 and 19 wt. %. Further, after mixing, it ispreferable to enough agitate the cellulose triacetate. Other materialsmay be added, for example, plasticizer, deterioration inhibitor, dynesand ultraviolet absorptive agent.

(Heating Process)

After swelling the cellulose triacetate particles, the mixed solutionsare preferably heated at a predetermined temperature over 130° C.,particularly over 160° C., and especially over 180° C. However over 250°C. , cellulose triacetate is discomposed, which causes to damage thefilm to be produced. An averaged difference of increased temperaturesper a minuet between start and end of heating is preferably more than 1°C./min., particularly more than 2° C./min., especially 4° C./min., andmore especially 8° C. /min, and upper limits thereof is theoretically10000° C./min., technically 1000° C./min., and practically 100° C./min.There are methods of heating, for example, autoclave, mutitube heatinterchanger, screw pressure and static mixer.

A time length for heating the mixed solution is preferably between 20seconds and 4 hours. When the time length is less than 20 seconds,unsolved materials remain in the dope solution. When filtration of theunsolved materials is carried out, a filtration life becomes shorter.The time length starts to be counted when the temperature reaches thepredetermined temperature, and ends to be counted when the temperaturebecome lower than the predetermined temperature.

(Pressure-Applying Process)

Preferably, the mixture solution is heated thereby under applyingpressure so as to prevent the solvent from boiling, and the temperaturethereof is more than a boiling point under atmospheric pressure. Thus,the dope solution can have uniformity of quality. The pressure to beapplied is adjusted in relation of the temperature of the solution tothe boiling point of the solvent.

(Cooling Process)

When the cellulose triacetate hardly solves in the solvent and remainsas unsolvable material in the solution, the solutions may be cooledbetween −100 and −10° C. before or after being heated, so as to obtainthe film having a good photographic character. When the mixture solutionis cooled down, the solvent penetrates in the cellulose triacetatesmoothly. Whether cellulose triacetate solves enough, it can beperceived with eyes. When it does not solve enough, the heating processand the cooling process are repeated. Note that in the cooling process,in order to prevent a mixture of water in the mixed solvent, a vessel tobe used is preferably tightly-closed. Further, when the pressure is madelower in the cooling process, the temperature becomes lower in shortertime. Accordingly, the vessel is preferably pressure-tight.

(Relation of Shearing Viscosities)

In order to prevent the generation of the skinning on an lip of the die,A/B and A′/B are preferably under 0.9 when A, A′ and B are respectivelydetermined as a shearing viscosity of the solution 33 a for the frontlayer 31 a, that of the solution 33c for the rear layer 31 c and that ofthe solution 33 b for the intermittent layer 33 b. The shearingviscosities A, A′ are between 30 and 50 Pa·S and the shearing viscosityB is between 10 and 150 Pa·S, when a shearing velocity is between 1 and3000 (1/sec) and the temperature for producing the film is between 30and 40° C. Note that, when the intermittent layer is constructed ofplural layers, the shearing viscosity B is an average of shearingviscosities of the plural layers.

[Products]

The film produced in the method described above is used as a deflectorfilm. Further, the film is used as the optical compensation film when anoptical compensation sheet is attached on the film.

Experiment 1

(Preparation of Solution Composing Dope Solution)

In Experiment 1 a solution S1 is used for the intermittent layer andmade from following compounds in the above-described method forpreparing the dope solution.

cellulose triacetate 100 part by weight triphenylphosphate 7.8 part byweight biphenyldiphenylphosphate 3.9 part by weight (plasticiser)methylenchloride (first solvent) 300 part by weight methanol (secondsolvent) 65 part by weight ultraviolet absorptive agent 1.0 part byweightNote that the cellulose triacetate used in Experiment 1 has 60.9% ofacetification degree. The solid content density of the solution S1 is23.4 wt. %, and the additives are mixed in ratio of 13 wt. % to thecellulose triacetate.

In Experiment 1 a solution S2 is used for the surface layer, and madefrom the following compounds.

cellulose triacetate 87 part by weight triphenylphosphate 6.8 part byweight biphenyldiphenylphosphate 3.4 part by weight (plasticiser)methylenchloride (first solvent) 300 part by weight methanol (secondsolvent) 65 part by weight ultraviolet absorptive agent 0.9 part byweightThe solid content density of the solution S2 is 21.0 wt. %, and theadditives are mixed in ratio of 13 wt. % to the cellulose triacetate.

In Experiment 1, a solution S3 is also used for the surface layer, andmade from the following compounds.

cellulose triacetate 77 part by weight triphenylphosphate 6.0 part byweight biphenyldiphenylphosphate 3.0 part by weight (plasticiser)methylenchloride (first solvent) 300 part by weight methanol (secondsolvent) 65 part by weight ultraviolet absorptive agent 0.9 part byweight

The solid content density of the solution S3 is 19.0 wt. %, and theadditives are mixed in ratio of 13 wt. % to the cellulose triacetate.

(Condition for Feeding Solvent)

The solvent fed to the end of the slit of the die is a mixture ofmethanol (bad solvent to the cellulose triacetate) and methylenchloride(good solution to the cellulose triacetate) in ratio of 50:50. Thesolvent is fed in the feeding velocity of 0.2 ml/min.

Embodiment 1

In Embodiment 1 (E1 ), the solution S2 is used for the surface layers.In producing the film, the die 4 of the feed block type is used. Thefilm is formed such that the averaged thickness of the film after dryingthe dope solution may be 60 μm, (S1+S2)D×100 may be 5%, and ratio (A/B)may be 0.72 when A and B are the shearing viscosity of the solution forthe surface layer and that of the solution for the intermittent layerrespectively.

Embodiment 2

In Embodiment 2 (E2), the film is produced in the same condition as inEmbodiment 1, except that (S1+S2)D×100 is 30%.

Embodiment 3

In Embodiment 3 (E3), the solution S3 is used for the surface layer. Inproducing the film, the die 4 is used. The film is formed such that theaveraged thickness of the film after drying the solutions may be 60 μm,(S1+S2)D×100 may be 30%, and the ratio (A/B) may be 0.52.

Embodiment 4

In Embodiment 4 (E4), mixture solvent is fed to the end of the die inpreparation of the film. Other condition is as same as in Embodiment 4.

Comparision 1

In Comparision 1 (C1), the film is formed only of the solution S1. Inthis case, (S1+S2)D×100 is 0, and the ratio A/B is 1. Other conditionsare as same as in Embodiment 1.

Comparision 2

In Comparision 2 (C2), the mixture solvent is fed to the end of the diein preparation of the film. Other condition is as same as in Embodiment1.

Evaluation 1

Evaluation of the film is made to generation frequency of skinning asfollows:

The skinning generates in few days N The skinning generates after morethan a month U The skinning generates after more than three months G Theskinning generates after more than six months B Herein N, U, G, B mean“not usable”, “usable”, “good” and “best”respectively.

Evaluation 2

Evaluation of surface situation of film is made as follows:

Worse than the limitation of usable quality N As same as the limitationof usable quality U More than the limitation of usable quality G HereinN, U, G mean “not usable”, “usable” and “good” respectively.

TABLE 1 E1 E2 E3 E4 C1 C2 Solution for surface S2 S2 S3 S3 — — layer(S1 + S2)/D (%) 5 30 30 30 0 0 A/B 0.72 0.72 0.52 0.52 1 1 Feedingsolvent No No No Yes No Yes Evaluation 1 G G G B N B Evaluation 2 U G GG N U

The results shown in Table 1 teaches that the film becomes better whenit is formed of the solution S3 having a lower solid content densitythan the solution S2. Accordingly, the dope solution used for producingthe film preferably has the lower solid content density. Further, whenthe mixture solvent is fed to the end of the die, the quality of thefilm becomes higher.

Experiment 2

In Experiment 2, methylacetate is used as the main solvents of the dopesolution. Evaluations of the embodiments 5-8 and Comparisions 3,4 are assame as those of Embodiment 1-5 and Comparisions 1,2.

Preparation of Solution Composing Dope Solution

In Experiment 2, a solution S4 is used for the intermittent layer, andmade from following compounds in the above-described method forpreparing the solution S4.

cellulose triacetate 100 part by weight triphenylphosphate 7.8 part byweight biphenyldiphenylphosphate 3.9 part by weight (plasticiser) methylacetate (first solvent) 260 part by weight mixture solvent (secondsolvent) 110 part by weight ultraviolet absorptive agent 0.9 part byweightThe mixture solvent of the second solvent contains acetone, ethanol,methanol, n-butanol in ratio 2:1:1:1. The solid content density of thesolution S4 is 23.4 wt. %, and the additives are mixed in ratio of 13wt. % to the cellulose triacetate.

In Experiment 2, a solution S5 is used for the surface layer, and madefrom the following compounds.

cellulose triacetate 87 part by weight triphenylphosphate 6.8 part byweight biphenyldiphenylphosphate 3.4 part by weight (plasticiser)methylenchloride (first solvent) 265.5 part by weight methanol (secondsolvent) 113.6 part by weight ultraviolet absorptive agent 0.9 part byweightThe solid content density of the solution S5 is 20.6 wt. %, and theadditives are mixed in ratio of 13 wt. % to the cellulose triacetate.

In Experiment 2, a solution S6 is used for the surface layer is madefrom the following compounds.

cellulose triacetate 77 part by weight triphenylphosphate 6.0 part byweight biphenyldiphenylphosphate 3.0 part by weight (plasticiser) methylacetate (first solvent) 266.5 Part by weight mixture solvent (secondsolvent) 114.3 part by weight ultraviolet absorptive agent 0.9 part byweight

The solid content density of the solution S6 is 18.6 wt. %, and theadditives are mixed in ratio of 13 wt. % to the cellulose triacetate.

Embodiment 5

In Embodiment 5 (E5), the solution S4 is used for the surface layers. Inproducing the film, a die of the feed block type is used. The film isformed such that the averaged thickness of the film after drying thedope solutions may be 60 μm, (S1+S2)D×100 may be 5%, and the ratio A/Bmay be 0.68.

Embodiment 6

In Embodiment 6 (E6), the film is produced in the same condition as inEmbodiment 5, except that (S1+S2)D×100 is 25%.

Embodiment 7

In Embodiment 7 (E7), the solution S6 is used for the surface layer. Inproducing the film, a die of the feed block type is used. The film isformed such that the averaged thickness of the film after drying thesolution S6 may be 60 mm, (S1+S2)D×100 may be 25%, and the ratio A/B maybe 0.47.

Embodiment 8

In Embodiment 8 (E8), mixture solvent is fed to the end of the die inpreparation of the film. Other condition is as same as in Embodiment 7.

Comparision 3

In Comparision 3 (C3), the film is formed only of the solution S4. Inthis case, (S1+S2)D×100 is 0%, and the ratio A/B is 1. Other conditionsare as same as in embodiment 5.

Comparision 4

In Comparision 4 (C4), the mixture solvent is fed to the end of the diein preparation of the film. Other condition is as same as in Embodiment3.

TABLE 2 E5 E6 E7 E8 C3 C4 Solution for surface S5 S5 S6 S6 — — layer(S1 + S2)/D (%) 5 25 25 25 0 0 A/B 0.68 0.68 0.47 0.47 1 1 Feedingsolvent No No No Yes No Yes Evaluation 1 G G G B N B Evaluation 2 U G GG N G

The results shown in Table 2 is almost as same as that in the Table 1.The methylenechloride harmfully influences on circumstance. Accordingly,the present invention is carried out by using methylacetate which has noinfluence on circumstance so much.

Experiment 3

In Experiment 3 chloride solvents are used in the dope solution. To thedope solution, a 40° C. warm air is blown to form the film whose totalthickness is 80 μm, and after peeled from the supporter, the film isdried in 120° C. for 10 minutes.

Embodiment 9

In Embodiment 9 (E9), the film is produced so as to have only one layer.

Embodiment 10

In Embodiment 10 (E10), the film is produced by using the die 4illustrated in FIG. 4 so as to have three layers.

Embodiment 11

In Embodiment 11 (E11), the film is produced by using the die 4illustrated in FIG. 4 so as to have two layers.

Embodiment 12

In Embodiment 12 (E12), the film is produced so as to have only onelayer.

Embodiment 13

In Embodiment 13 (E13), the film is produced by using the die 4illustrated in FIG. 4 so as to have three layers.

Embodiment 14

In Embodiment 14 (E14), the film is produced by using the die 4illustrated in FIG. 4 so as to have three layers.

Comparision 5

In Comparision 5 (C5), the film is produced so as to have only onelayer.

In Experiments 9-14 and Comparision 5, following solutions 7-11 areused. The composition of the each solution in the dope solution is asfollows.

<Solution 7 (S7)> cellulose triacetate 23 parts by weight Ratio ofmasses (cotton linter/wood pulp = 60/40) triphenylphosphate 3 parts byweight mixture solvent 74 part by weight Ratio of masses(dichloromethane/methanol = 77/23) <Solution 8 (S8)> cellulosetriacetate 23 parts by weight Ratio of masses (cotton linter/wood pulp =0/100) triphenylphosphate 3 parts by weight mixture solvent 74 part byweight Ratio of masses (dichloromethane/methanol = 77/23) <Solution 9(S9)> cellulose triacetate 20 parts by weight Ratio of masses (cottonlinter/wood pulp = 0/100) triphenylphosphate 3 parts by weight mixturesolvent 77 part by weight Ratio of masses (dichloromethane/methanol =77/23) <Solution 10 (S10)> cellulose triacetate 23 parts by weight Ratioof masses (cotton linter/wood pulp = 0/100) triphenylphosphate 3 partsby weight mixture solvent 74 part by weight Ratio of masses(dichloromethane/methanol = 76/24) <Solution 11 (S11)> cellulosetriacetate 23 parts by weight Ratio of masses (cotton linter/wood pulp =0/100) triphenylphosphate 3 parts by weight mixture solvent 74 part byweight Ratio of masses (dichloromethane/methanol = 77/23) Citric acid(mold releasing accelerator) 300 PPM in weight of the solution S11.

(Method of Forming Deflector)

Polyvinyl alcohol film (75 μm) is set in iodine/potassium iodidesolution and boric acid solution sequentially, and thereafter extendedin a lengthwise direction of the film. Then the film is dried to formthe polarizer.

Further, the film is set in alkali solution, acid solution and watersequentially. Thereafter the film is dried, and the process of thesurface of the film is carried out. Then the film is adhered to thepolarizer and dried again.

(Forming Estimation Panel for Estimation Frame)

An adhesive agent is applied to a surface of the deflector cut in sizeof 15 inches. Then the deflector is adhered to the both surfaces of asoda glass to form an estimation panel such that orientation axes of thedeflector and the soda glass are perpendicular to each other.

(Estimation of Frame)

The estimation panel is processed in 40° C. and 95% atmosphere for 17hours, and thereafter set in the room temperature for 24 hours.Thereafter, the estimation panel is disposed on a schaukasten, andoptical creases are estimated with eyes as follows

AA: there are no optical creases (best)

A: there are few obvious optical creases in edges of the frame (good)

B: there are distinct creases in the edges of the frame (usable)

C: there are creases also in a central part of the frame (unusable)

The result of Experiment 1 is shown in Table 3. In Table 3, L1, L2, L3are respectively the uppermost, intermittent and lowest layers of thedope solution on the supporter. Further, H1, H2, H3 are respectivelythickness of layers formed from the uppermost, intermittent, and lowestlayers of the dope solution after dried. EV is ratio of the evaporatedsolvents to the film just after peeled from the supporter.

TABLE 3 Thickness Estimation Composition of dope ratio EV 13 20 L1 L2 L3H1 H2 H3 Wt % inch inch E9 S8 S8 S8 — — — 100 A B E10 S8 S7 S8 5 70 5100 A B E11 S8 S8 S11 — 75 5 200 AA AA E12 S8 S8 S8 — — — 140 AA A E13S9 S8 S9 5 70 5 100 AA A E14 S8 S8 S10 5 70 5 160 AA A C5 S7 S7 S7 — — —100 B C

Experiment 4

In Experiment 4 non-chloride solvents are used in the dope solution. Tothe dope solution, a 60° C. warm air is blown to form the film whosetotal thickness is 80 μm, and after peeled from the supporter, the filmis dried in 120° C. for 10 minutes.

Embodiment 15

In Embodiment 15 (E15), the film is produced so as to have only a singlelayer.

Embodiment 16

In Embodiment 16 (E16), the film is produced by using the die 40 so asto have three layers.

Embodiment 17

In Embodiment 17 (E17), the film is produced by using the die 40 so asto have two layers.

Embodiment 18

In Embodiment 18 (E18), the film is produced so as to have only a singlelayer.

Embodiment 19

In Embodiment 19 (E19), the film is produced by using the die 40illustrated in FIG. 7 so as to have three layers.

Embodiment 20

In Embodiment 20 (E20), the film is produced by using the dies 50 a , 50b, 50 c illustrated in FIG. 8 so as to have three layers.

Comparision 6

In Comparision 5 (C5), the film is produced so as to have only a singlelayer.

In Experiments 15-20 and Comparision 6, following solutions 12-16 areused. The composition of each solution in the solution is as follows.

<Solution 12 (S12)> cellulose triacetate 22 parts by weight Ratio ofmasses (cotton linter/wood pulp = 60/40) triphenylphosphate 3 parts byweight mixture solvent 74 part by weight Ratio of masses (methylacetate/acetone/alcohol = 45/20/15) <Solution 13 (S13)> cellulosetriacetate 22 parts by weight Ratio of masses (cotton linter/wood pulp =0/100) triphenylphosphate 3 parts by weight mixture solvent 74 part byweight Ratio of masses (methyl acetate/acetone/alcohol = 45/20/15)<Solution 14 (S14)> cellulose triacetate 20 parts by weight Ratio ofmasses (cotton linter/wood pulp = 0/100) triphenylphosphate 3 parts byweight mixture solvent 77 part by weight Ratio of masses (methylacetate/acetone/alcohol = 45/20/15) <Solution 15 (S15)> cellulosetriacetate 22 parts by weight Ratio of masses (cotton linter/wood pulp =0/100) triphenylphosphate 3 parts by weight mixture solvent 74 part byweight Ratio of masses (methyl acetate/acetone/alcohol = 44/20/16)<Solution 16 (S16)> cellulose triacetate 23 parts by weight Ratio ofmasses (cotton linter/wood pulp = 0/100) triphenylphosphate 3 parts byweight mixture solvent 74 part by weight Ratio of masses (methylacetate/acetone/alcohol = 45/20/15) Citric acid (mold releasingaccelerator) 300 PPM in weight of the solution S11.

In Experiment 4, the estimation panel is made and the estimation of iscarried out as same as in Experiment 3.

TABLE 4 Composition of dope Thickness Estimation solution ratio EV 13 20L1 L2 L3 H1 H2 H3 wt % inch inch E15 S13 S13 S13 — — — 100 A B E16 S13S12 S13 5 70 5 100 A B E17 S13 S13 S11 — 75 5 200 AA AA E18 S13 S13 S13— — — 140 AA A E19 S14 S13 S14 5 70 5 100 AA A E20 S13 S13 S15 5 70 5160 AA A C6 S12 S12 S12 — — — 100 B C

Various changes and modifications are possible in the present inventionand may be understood to be within the present invention.

1. A method of producing a cellulose ester film having a front layer, anintermediate layer and a rear layer by using a dope solution, saidfront, intermediate, and rear layers being respectively formed of first,second and third solutions which construct said dope solution, saidmethod comprising a step of: doping said dope solution from a die havinga slit on a supporter, in said dope solution a solid content density ofeach of said first and third solutions being lower than that of saidsecond solution, and satisfying a condition that A/B is under 0.9,wherein A and B are a shearing viscosity of said first solution or saidthird solution and a shearing viscosity of said second solutionrespectively, wherein when said dope solution is doped as a dope ribbonfrom said die, a total thickness of edges of said front layer and saidrear layer is more than 5% of a total thickness of said dope ribbon; andfeeding a mixture solvent from both sides of a slit of said die, saidmixture solvent containing a good solution and a bad solution to solutesin said dope solution.
 2. A method according to claim 1, wherein saidintermediate layer is constituted of plural layers.
 3. A methodaccording to claim l, wherein said first solution, said second solutionand said third solution are doped in a superposed situation on saidsupporter, or sequentially doped on said supporter.
 4. A methodaccording to claim 2, wherein said die is provided with a feed block forsuperposing said first, second and third solutions in a smaller widththan said dope solution so as to said first, second, third solutions assaid dope solution into said die.
 5. A method according to claim 3,wherein said die is provided with a feed block for superposing saidfirst, second and third solutions in a smaller width than said dopesolution so as to said first, second, third solutions as said dopesolution into said die.
 6. A method according to claim 2, wherein saiddie includes three manifolds for containing said first, second and thirdsolutions respectively.
 7. A method according to claim 3, wherein saiddie includes three manifolds for containing said first, second and thirdsolutions respectively.
 8. A method according to claim 1, wherein saidmixture solvent contains a bad solution of 30-90 wt.% to solutes in saiddope solution.
 9. A method according to claim 1, wherein a thickness ofsaid cellulose ester film formed by drying said dope solution is 20-200μm.
 10. A method according to claim 9, wherein said cellulose ester filmis used as deflector film.
 11. A method according to claim 9, whereinsaid cellulose ester film is uses as an optical compensation film.